Cosmology II: The thermal history of the Universe . Ruth Durrer - - PowerPoint PPT Presentation
. Cosmology II: The thermal history of the Universe . Ruth Durrer Dpartement de Physique Thorique et CAP Universit de Genve Suisse August 6, 2014 . . . . . . Ruth Durrer (Universit de Genve) Cosmology II August 6, 2014 1
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Ruth Durrer
Département de Physique Théorique et CAP Université de Genève Suisse
August 6, 2014
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 1 / 21
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The thermal history of the Universe . .
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The cosmic microwave background . .
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Dark matter . .
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Dark energy models . .
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Conclusions
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 2 / 21
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In the past the Universe was not only much denser than today but also much hotter. Age of the Universe: t0 ≃ 13.7 billion years The most remarkable events
Recombination (electrons and protons combine to neutral hydrogen).
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 3 / 21
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In the past the Universe was not only much denser than today but also much hotter. Age of the Universe: t0 ≃ 13.7 billion years The most remarkable events
Recombination (electrons and protons combine to neutral hydrogen). Nucleosyhthesis (the formation of Helium, Deuterium, ...)
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 3 / 21
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In the past the Universe was not only much denser than today but also much hotter. Age of the Universe: t0 ≃ 13.7 billion years The most remarkable events
Recombination (electrons and protons combine to neutral hydrogen). Nucleosyhthesis (the formation of Helium, Deuterium, ...) Inflation ?
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 3 / 21
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Since the photon (radiation) energy density scales like T 4 ∝ R−4 ∝ (z + 1)4 while the matter density scales like mn ∝ R−3 ∝ (z + 1)3, at very early time, the Universe is radiation dominated (z > ∼ 4000, t < ∼ 104 years).
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 4 / 21
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Since the photon (radiation) energy density scales like T 4 ∝ R−4 ∝ (z + 1)4 while the matter density scales like mn ∝ R−3 ∝ (z + 1)3, at very early time, the Universe is radiation dominated (z > ∼ 4000, t < ∼ 104 years). At T ≃ 3000K (t ≃ 300′000years) the Universe is ’cold’ enough that protons and electrons can combine to neutral hydrogen.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 4 / 21
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Since the photon (radiation) energy density scales like T 4 ∝ R−4 ∝ (z + 1)4 while the matter density scales like mn ∝ R−3 ∝ (z + 1)3, at very early time, the Universe is radiation dominated (z > ∼ 4000, t < ∼ 104 years). At T ≃ 3000K (t ≃ 300′000years) the Universe is ’cold’ enough that protons and electrons can combine to neutral hydrogen. After this, photons no longer scatter with matter but propagate freely. Their energy (and hence the temperature) is redshifted to T0 = 2.728K today, corresponding to a density of about 400 photons per cm3.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 4 / 21
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Since the photon (radiation) energy density scales like T 4 ∝ R−4 ∝ (z + 1)4 while the matter density scales like mn ∝ R−3 ∝ (z + 1)3, at very early time, the Universe is radiation dominated (z > ∼ 4000, t < ∼ 104 years). At T ≃ 3000K (t ≃ 300′000years) the Universe is ’cold’ enough that protons and electrons can combine to neutral hydrogen. After this, photons no longer scatter with matter but propagate freely. Their energy (and hence the temperature) is redshifted to T0 = 2.728K today, corresponding to a density of about 400 photons per cm3. This cosmic microwave background can be observed today in the (1– 400)GHz
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 4 / 21
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Since the photon (radiation) energy density scales like T 4 ∝ R−4 ∝ (z + 1)4 while the matter density scales like mn ∝ R−3 ∝ (z + 1)3, at very early time, the Universe is radiation dominated (z > ∼ 4000, t < ∼ 104 years). At T ≃ 3000K (t ≃ 300′000years) the Universe is ’cold’ enough that protons and electrons can combine to neutral hydrogen. After this, photons no longer scatter with matter but propagate freely. Their energy (and hence the temperature) is redshifted to T0 = 2.728K today, corresponding to a density of about 400 photons per cm3. This cosmic microwave background can be observed today in the (1– 400)GHz
It represents a ’photo’ of the Universe when it was about 300’000 years old, corresponding to a redshift of z ≃ 1100.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 4 / 21
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(Fixen et al. 1996) Nobel Prize 1978 for Penzias and Wilson, Nobel Prize 2006 for Mather T0 = 2.728K ≃ −270.5oC
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 5 / 21
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Smoot et al. (1999), Nobel Prize 2006 Map of the CMB temperature: per- fectly isotropic. Subtracting the monopole a dipole
the sphere of emission (last scatter- ing surface). And what is this? Left over after subtracting the dipole. Fluctuations
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 6 / 21
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ESA/Planck (2013)
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 7 / 21
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2 10 50 1000 2000 3000 4000 5000 6000
D[µK2]
90 18 500 1000 1500 2000 2500
Multipole moment,
1 0.2 0.1 0.07
Angular scale
ESA/Planck (2013) ℓ = 200 corresponds to about 1o. ⇒ ’acoustic’ peaks. (θ ≃ 180o/ℓ) (This is roughly the double of the angular size of the full moon (or of the sun).)
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 8 / 21
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The matter distribution in the observed Universe is not very homogeneous and isotropic. It is in form of galaxies, clusters, filaments, voids. The idea is that these large scale structures formed by gravitational instability from small initial fluctua- tions which have been set up during inflation.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 9 / 21
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The matter distribution in the observed Universe is not very homogeneous and isotropic. It is in form of galaxies, clusters, filaments, voids. The idea is that these large scale structures formed by gravitational instability from small initial fluctua- tions which have been set up during inflation. These initial fluctuations are also imprinted in the CMB.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 9 / 21
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The matter distribution in the observed Universe is not very homogeneous and isotropic. It is in form of galaxies, clusters, filaments, voids. The idea is that these large scale structures formed by gravitational instability from small initial fluctua- tions which have been set up during inflation. These initial fluctuations are also imprinted in the CMB. Once a given scale enters the horizon, fluctuations on this scale begin to oscillate like acoustic waves (sound). The first peak corresponds to fluctuations which have had time to make exactly 1 contraction since horizon entry until decoupling.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 9 / 21
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The matter distribution in the observed Universe is not very homogeneous and isotropic. It is in form of galaxies, clusters, filaments, voids. The idea is that these large scale structures formed by gravitational instability from small initial fluctua- tions which have been set up during inflation. These initial fluctuations are also imprinted in the CMB. Once a given scale enters the horizon, fluctuations on this scale begin to oscillate like acoustic waves (sound). The first peak corresponds to fluctuations which have had time to make exactly 1 contraction since horizon entry until decoupling. The second peak peak corresponds to fluctuations which have had time to make exactly 1 contraction and 1 expansion since horizon entry until decoupling (under density).
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 9 / 21
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The matter distribution in the observed Universe is not very homogeneous and isotropic. It is in form of galaxies, clusters, filaments, voids. The idea is that these large scale structures formed by gravitational instability from small initial fluctua- tions which have been set up during inflation. These initial fluctuations are also imprinted in the CMB. Once a given scale enters the horizon, fluctuations on this scale begin to oscillate like acoustic waves (sound). The first peak corresponds to fluctuations which have had time to make exactly 1 contraction since horizon entry until decoupling. The second peak peak corresponds to fluctuations which have had time to make exactly 1 contraction and 1 expansion since horizon entry until decoupling (under density). The third peak corresponds to fluctuations which have had time to make exactly 2 contractions (and 1 expansion) since horizon entry until decoupling. · · ·
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 9 / 21
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Planck WMAP9 ACT SPT
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 10 / 21
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The patches which have of peak ampli- tude temperature fluctuations are stan- dard rulers. Their size is given by the age
(recombination). The angle under which we see these patches determines the dis- tance to the surface of last scattering. (z = zdec ≃ 1100), d = r/θ. The amplitude of the peaks depends on the matter density ρm ∝ ΩmH2
0 = (13 ± 2) × 100(km/s/Mpc)2
and the difference of the amplitude of even and odd peaks depends strongly on the density of electrons and hence baryons, ρb ∝ ΩbH2
0 = 2.2 ± 0.3 × 100(km/s/Mpc)2
≪ ΩmH2
0.
Most of the matter in the Universe is dark and non-baryonic! r d θ
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 11 / 21
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The acoustic peaks are also visible in the matter power spectrum. (= The mean square amplitude of fluctuations of a given size.) from Anderson et al. ’12 SDSS-III (BOSS) power spectrum.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 12 / 21
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Data: CMB + BAO + SN Ia H0 = 67.8 ± 1km/s/Mpc = h100km/s/Mpc Ωm = 0.31 ± 0.01 Ωbh2 = 0.0221 ± 0.0002 ΩK = −0.0005+0:0065
−0.0066
ΩΛ = 0.69 ± 0.01 Ωradh2 = 0.48 × 10−5 age = 13.80 ± 0.04Gyr
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 13 / 21
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Most of the matter in the Universe is in the form of an unknown non-baryonic component which does not interact with photons (dark).
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 14 / 21
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Most of the matter in the Universe is in the form of an unknown non-baryonic component which does not interact with photons (dark). Also most of the baryonic matter is in the form of gas which does not emit light.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 14 / 21
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Most of the matter in the Universe is in the form of an unknown non-baryonic component which does not interact with photons (dark). Also most of the baryonic matter is in the form of gas which does not emit light. The first to postulate dark matter was the Swiss astronomer Fritz Zwicky. He realized that binding galaxy clusters gravitationally, requires about 100 times more mass than the mass of all its stars (HPA, 1933). In the 70ties, the American astronomer Vera Rubin has shown that also galaxies are dominated by dark matter which contributes about 10 times more to their mass than the stars.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 14 / 21
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Rubin found that the rotation curves of test particles (stars, hydrogen atoms) rotating around galaxies do not show the expected decay of the velocity, v 2 = GM r , v ∝ 1 √r but have v = constant. Kepler’s law then requires that M ∝ r.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 15 / 21
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These original discoveries do not shed any light on the nature of dark matter except that it does not emit visible photons.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 16 / 21
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These original discoveries do not shed any light on the nature of dark matter except that it does not emit visible photons. X ray observations show that a part (about 10% ) of dark matter in clusters is in the form of hot gas emitting X rays.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 16 / 21
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These original discoveries do not shed any light on the nature of dark matter except that it does not emit visible photons. X ray observations show that a part (about 10% ) of dark matter in clusters is in the form of hot gas emitting X rays. Estimations of cluster masses (and CMB and LSS observations) yield Ωmh2 ≃ 0.14
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 16 / 21
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These original discoveries do not shed any light on the nature of dark matter except that it does not emit visible photons. X ray observations show that a part (about 10% ) of dark matter in clusters is in the form of hot gas emitting X rays. Estimations of cluster masses (and CMB and LSS observations) yield Ωmh2 ≃ 0.14 CMB anisotropies (and nucleosynthesis) require Ωbh2 ≃ 0.02
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 16 / 21
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These original discoveries do not shed any light on the nature of dark matter except that it does not emit visible photons. X ray observations show that a part (about 10% ) of dark matter in clusters is in the form of hot gas emitting X rays. Estimations of cluster masses (and CMB and LSS observations) yield Ωmh2 ≃ 0.14 CMB anisotropies (and nucleosynthesis) require Ωbh2 ≃ 0.02 Hence most of dark matter (env. 85%) is non-baryonic.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 16 / 21
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What could this dark matter be?
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons. Neutrino (cannot be bound in dwarf galaxies, too little small scale structure).
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons. Neutrino (cannot be bound in dwarf galaxies, too little small scale structure). Sterile Neutrino which is more massive but less abundant ?
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons. Neutrino (cannot be bound in dwarf galaxies, too little small scale structure). Sterile Neutrino which is more massive but less abundant ? Neutralino (stable particle in most simple models of super-symmetry ⇒ LHC) ?
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons. Neutrino (cannot be bound in dwarf galaxies, too little small scale structure). Sterile Neutrino which is more massive but less abundant ? Neutralino (stable particle in most simple models of super-symmetry ⇒ LHC) ? Axion (Hypothetical stable particle required to solve the ’strong CP problem’) ?
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons. Neutrino (cannot be bound in dwarf galaxies, too little small scale structure). Sterile Neutrino which is more massive but less abundant ? Neutralino (stable particle in most simple models of super-symmetry ⇒ LHC) ? Axion (Hypothetical stable particle required to solve the ’strong CP problem’) ? Primordial black holes ?
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons. Neutrino (cannot be bound in dwarf galaxies, too little small scale structure). Sterile Neutrino which is more massive but less abundant ? Neutralino (stable particle in most simple models of super-symmetry ⇒ LHC) ? Axion (Hypothetical stable particle required to solve the ’strong CP problem’) ? Primordial black holes ? Wimpzillas ?
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons. Neutrino (cannot be bound in dwarf galaxies, too little small scale structure). Sterile Neutrino which is more massive but less abundant ? Neutralino (stable particle in most simple models of super-symmetry ⇒ LHC) ? Axion (Hypothetical stable particle required to solve the ’strong CP problem’) ? Primordial black holes ? Wimpzillas ? Gravitinos ?
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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What could this dark matter be? A stable particle which do not couple to photons. Neutrino (cannot be bound in dwarf galaxies, too little small scale structure). Sterile Neutrino which is more massive but less abundant ? Neutralino (stable particle in most simple models of super-symmetry ⇒ LHC) ? Axion (Hypothetical stable particle required to solve the ’strong CP problem’) ? Primordial black holes ? Wimpzillas ? Gravitinos ? All these candidates require physics beyond the standard model!
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 17 / 21
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Cosmological constant / vacuum energy Provides a good fit to the data, but nobody understands its value and which it comes to dominate exactly ’now’.
1 2 3 4
4)]
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 18 / 21
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Quintessence A scalar field which first follows the scaling of matter and radiation and has started to dominate recently.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 19 / 21
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Quintessence A scalar field which first follows the scaling of matter and radiation and has started to dominate recently. Can reproduce the data if its behavior is close to a cosmological constant.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 19 / 21
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Quintessence A scalar field which first follows the scaling of matter and radiation and has started to dominate recently. Can reproduce the data if its behavior is close to a cosmological constant.
0.0 0.1 0.2 0.3 0.4 0.5
0.0
SNe BAO CMB ΩM
w w = P/ρE =pressure/(energy density)
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 19 / 21
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Modification of gravity at large scales, e.g. massive gravity, degravitation, extra dimensions.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 20 / 21
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Modification of gravity at large scales, e.g. massive gravity, degravitation, extra dimensions. Backreaction: If structure formation leads to relevant modifications of the geometry, this could modify the relation between distance and redshift...
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 20 / 21
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Observations SN 15 years after the discovery of the accelerated expansion of the Universe,
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 21 / 21
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Observations SN 15 years after the discovery of the accelerated expansion of the Universe,
Other data also require dark energy CMB, BAO, ....
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 21 / 21
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Observations SN 15 years after the discovery of the accelerated expansion of the Universe,
Other data also require dark energy CMB, BAO, .... Cosmological constant A cosmological constant or vacuum energy which contributes about 70% to the energy density of the Universe is in good agreement with data.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 21 / 21
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Observations SN 15 years after the discovery of the accelerated expansion of the Universe,
Other data also require dark energy CMB, BAO, .... Cosmological constant A cosmological constant or vacuum energy which contributes about 70% to the energy density of the Universe is in good agreement with data. Dark matter 25% of the energy density of the Universe is in the form of non-baryonic dark
identify dark matter 80 years after it has been first postulated by Fritz Zwicky.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 21 / 21
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Observations SN 15 years after the discovery of the accelerated expansion of the Universe,
Other data also require dark energy CMB, BAO, .... Cosmological constant A cosmological constant or vacuum energy which contributes about 70% to the energy density of the Universe is in good agreement with data. Dark matter 25% of the energy density of the Universe is in the form of non-baryonic dark
identify dark matter 80 years after it has been first postulated by Fritz Zwicky. Baryons Only about 5% of the energy density of the present Universe is in the form of matter as we find it in our solar system, ordinary atoms made out of baryons and electrons.
Ruth Durrer (Université de Genève) Cosmology II August 6, 2014 21 / 21